(1) Field of the Invention
The present invention relates to fluid propulsion devices and in particular, to a fluid propulsion device that discharges working fluid at variable rates to accelerate a projectile.
(2) Description of the Prior Art
One way of launching projectiles is with a working fluid capable of storing potential energy that is converted to kinetic energy, causing the working fluid to accelerate the projectile. Some existing projectile launching systems include ram pump and turbine pump projection systems. Both such systems are mechanically complex and tend to radiate noise into the surrounding fluid medium during launching of the projectile.
Other systems have used elastomeric bladders for storing the potential energy of a working fluid. The working fluid expands the bladder, and upon contraction of the bladder, the fluid is released or discharged and causes acceleration of the projectile. The existing elastomeric bladders used to store potential energy of a working fluid have also met with a number of limitations.
Many existing elastomeric bladders utilize a non-compressible fluid, such as water, as disclosed in U.S. Pat. No. 5,200,572. This type of system only stores the potential energy in the elastomeric walls of the bladder. No energy is stored in the non-compressible working fluid, itself.
Existing projectile launching systems also have a limited ability to vary or define the desired discharge rate of the working fluid expelled or released from the elastomeric bladder. The inability to control the discharge rate of the working fluid expelled from the elastomeric bladder results in the inefficient conversion of potential energy to kinetic energy in launching a projectile. Moreover, the uncontrolled discharge of the working fluid in existing projectile launching systems causes an uncontrolled acceleration of the projectile, resulting in excessive noise, vibration, and inaccuracy of the launched projectile.
Existing pneumatic guns (or airguns), for example, propel their projectiles with a gas, supplied from either a gas cylinder or via a piston spring arrangement. Overdischarge of the gas causes a "blowby" of the discharging gas as the projectile is fired, thereby adversely affecting the projectile's trajectory path. This type of pneumatic gun also experiences a significant recoil when fired and significant noise or "blast" caused by the discharging gas leaving the barrel or bore of the projectile launcher. Underdischarge of the gas often causes deceleration of the projectile before exiting the barrel or bore of the gun.